Matplotlib errors result in a memory leak. How can I free up that memory?

I am running a django app that includes matplotlib and allows the user to specify the axes of the graph. This can result in 'Overflow Error: Agg complexity exceeded'

When that happens up to 100MB of RAM get tied up. Normally I free that memory up using fig.gcf(), plot.close(), and gc.collect(), but the memory associated with the error does not seem to be associated with the plot object.

Does anyone know how I can release that memory?

Thanks.

Here is some code that gives me the Agg Complexity Error.

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import numpy as np      
import gc

a = np.arange(1000000)
b = np.random.randn(1000000)

fig = plt.figure(num=1, dpi=100, facecolor='w', edgecolor='w')
fig.set_size_inches(10,7)
ax = fig.add_subplot(111)
ax.plot(a, b)

fig.savefig('yourdesktop/random.png')   # code gives me an error here

fig.clf()    # normally I use these lines to release the memory
plt.close()
del a, b
gc.collect()